Table Of ContentComputational
Colour Science
using MATLAB
Wiley-IS&T Series in Imaging Science and Technology
Series Editor:
Michael A. Kriss
Consultant Editor:
Lindsay W. MacDonald
Reproduction of Colour (6th Edition) The JPEG 2000 Suite
R.W.G. Hunt Peter Schelkens, Athanassios Skodras
and Touradj Ebrahimi (Eds.)
Colour Appearance Models (2nd Edition)
Mark D. Fairchild Color Management: Understanding and
Using ICC Profiles
Colorimetry: Fundamentals and
Phil Green (Ed.)
Applications
Noburu Ohta and Fourier Methods in Imaging
Alan R. Robertson Roger L. Easton, Jr.
Color Constancy Measuring Colour (4th Edition)
Marc Ebner R.W.G. Hunt and M.R. Pointer
Color Gamut Mapping The Art and Science of HDR Imaging
Ja´n Morovicˇ John McCann and Alessandro Rizzi
Panoramic Imaging: Sensor-Line Cameras Computational Colour Science using
and Laser Range-Finders MATLAB (2nd Edition)
Fay Huang, Reinhard Klette and Stephen Westland, Caterina Ripamonti
Karsten Scheibe and Vien Cheung
Digital Color Management (2nd Edition)
Edward J. Giorgianni and
Thomas E. Madden
Published in Association with the Society for Imaging Science and Technology
Computational
Colour Science
using MATLAB
Second edition
STEPHEN WESTLAND
University of Leeds, UK
CATERINA RIPAMONTI
University College London, UK
and
VIEN CHEUNG
University of Leeds, UK
A John Wiley & Sons, Ltd., Publication
(cid:1)c 2012,JohnWiley&Sons,Ltd
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LibraryofCongress Cataloguing-in-PublicationData
Westland,Stephen.
ComputationalcolourscienceusingMATLAB. – 2nded./StephenWestland,
CaterinaRipamonti,VienCheung.
p.cm.
Summary:“Describeshowtoimplementcolourscienceinawaythatmostothertexts
barelytouchupon”–Providedbypublisher.
Includes bibliographicalreferences andindex.
ISBN978-0-470-66569-5(hardback)
1.Colorimetry.2.MATLAB.I.Ripamonti,Caterina.II.Cheung,Vien,1977-III.Title.
QC495.8.W472012
535.60285(cid:2)53--dc23
2012009212
Acatalogue recordforthisbookisavailable fromtheBritishLibrary.
ISBN:978-0-470-66569-5
Setin10/12ptTimesbyLaserwordsPrivateLimited,Chennai,India
Contents
Acknowledgements ix
About the Authors xi
1. Introduction 1
1.1 Preface 1
(cid:1)
1.2 Why Base this Book on MATLAB ? 2
1.3 A Brief Review of the CIE System of Colorimetry 4
2. Linear Algebra for Beginners 13
2.1 Some Basic Definitions 13
2.2 Solving Systems of Simultaneous Equations 14
2.3 Function Approximation 16
(cid:1)
3. A Short Introduction to MATLABR 19
3.1 Matrices 19
3.2 Matrix Operations 21
3.3 Solving Linear Systems 23
3.4 M-Files 25
(cid:1)
3.5 Using Functions in MATLAB 25
4. Computing CIE Tristimulus Values 27
4.1 Introduction 27
4.2 Colour-Matching Functions 28
4.3 Interpolation Methods 29
4.4 Extrapolation Methods 38
4.5 Correction for Spectral Bandpass 38
4.6 Tristimulus Values 39
4.7 Chromaticity Diagrams 43
5. CIELAB and Colour Difference 49
5.1 Introduction 49
5.2 CIELAB and CIELUV Colour Space 50
(cid:1)
5.2.1 A Representation of CIELAB Using MATLAB 56
5.3 CIELAB Colour Difference 60
vi Contents
5.4 Optimised Colour-Difference Formulae 64
5.4.1 CMC (l:c) 64
5.4.2 CIE 94 67
5.4.3 CIEDE2000 68
6. Chromatic-Adaptation Transforms and Colour Appearance 75
6.1 Introduction 75
6.2 Chromatic-Adaptation Transforms (CATs) 76
6.2.1 A Brief History of CATs 80
6.2.2 CMCCAT97 80
6.2.3 CMCCAT2000 83
6.3 Colour-Appearance Models (CAMs) 86
6.3.1 CIECAM02 88
7. Physiological Colour Spaces 93
7.1 Introduction 93
7.2 Colour Vision 94
7.3 Cone-Excitation Space 96
7.4 MacLeod and Boynton Chromaticity Diagram 101
7.5 DKL Colour Space 106
8. Colour Management 119
8.1 The Need for Colour Management 119
(cid:1)
8.1.1 Using MATLAB to Create Representations of Gamuts 121
8.2 RGB Colour Spaces 122
8.2.1 sRGB 123
8.2.2 Adobe RGB (1998) 125
8.3 The International Color Consortium 126
8.4 Characterisation and Calibration 127
8.4.1 Approaches to Characterisation 128
9. Display Characterisation 131
9.1 Introduction 131
9.2 Gamma 131
9.3 The GOG Model 132
9.4 Device-Independent Transformation 133
9.5 Characterisation Example of CRT Display 134
9.6 Beyond CRT Displays 140
10. Characterisation of Cameras 143
10.1 Introduction 143
10.2 Correction for Nonlinearity 144
10.3 Correction for Lack of Spatial Uniformity 146
10.4 Characterisation 146
10.5 Example Characterisation of a Digital Camera 149
Contents vii
11. Characterisation of Printers 159
11.1 Introduction 159
11.1.1 Physical Models 160
11.1.2 Neural Networks 161
11.2 Characterisation of Half-Tone Printers 162
11.2.1 Correction for Nonlinearity 162
11.2.2 Neugebauer Models 163
11.2.3 Example Characterisation of a Half-Tone Printer 165
11.3 Characterisation of Continuous-Tone Printers 169
11.3.1 Kubelka-Munk Models 169
11.3.2 Interpolation of 3D Look-Up Tables 172
11.3.3 General Linear and Nonlinear Transforms 173
11.3.4 Example Characterisation
of a Half-Tone Printer 173
12. Multispectral Imaging 179
12.1 Introduction 179
12.2 Computational Colour Constancy and Linear Models 180
(cid:1)
12.2.1 Example Using MATLAB 181
12.3 Properties of Reflectance Spectra 182
12.3.1 PCA and SVD 183
(cid:1)
12.3.2 SVD Using MATLAB 185
12.4 Application of SVD to Reflectance Recovery 189
12.5 Techniques for Multispectral Imaging 191
12.5.1 Maloney-Wandell Method 191
12.5.2 Imai-Berns Method 192
12.5.3 Shi-Healey Method 193
12.5.4 Methods Based on Maximum Smoothness 193
12.5.5 Device Characterisation Revisited 193
12.6 Fourier Operations on Reflectance Spectra 193
A. Table of White Points of Illuminants used in r2xyz
and Other Functions 197
B. Colour Toolbox 199
B.1 Where to Find the Toolbox 199
B.2 How to Install the Toolbox 199
B.3 Summary of Toolbox Files 199
B.3.1 Computing CIE Tristimulus Values 199
B.3.2 CIELAB and Colour Difference 200
B.3.3 Chromatic-Adaptation Transforms and Colour
Appearance 200
B.3.4 Physiological Colour Spaces 200
B.3.5 Colour Management 200
B.3.6 Display Characterisation 200
viii Contents
B.3.7 Characterisation of Cameras 201
B.3.8 Characterisation of Printers 201
References 203
Index 213
Acknowledgements
This book makes extensive use of the MATLAB programme, which is distributed
by The MathWorks, Inc. We are grateful to The MathWorks for permission to include
extracts of this code.
For MATLAB product information, please contact:
The MathWorks, Inc.
3 Apple Hill Drive
Natick, MA 01760–2098, USA
Email: [email protected]
Web: www.mathworks.com
ThecodeinthisbookwasproducedwithBitstreamVeraSansMonospacedfont1.One
of the nice features of this font is that it clearly distinguishes between a zero (0) and a
capital O(O).Tousethisfont inMATLAB ,selecting theCustom itemunder Fonts in
the preferences tree. Select the component to change the font for, select the category of
font to change and finally select a font in the combo box.
TheauthorswouldliketothankDrPeterRhodesforhisadviceandcommentsregard-
ing methods to plot representations of the chromaticity diagram and for the use of the
DigiEyesystemsfortheimagesusedinthecasestudyofcameracharacterisation;Marjan
Vazirian for the colour measurements of the case study of CRT characterisation.
1Availablefromftp.gnome.org/pub/GNOME/sources/ttf-bitstream-vera/1.10/
About the Authors
Stephen Westland
Stephen Westland was awarded his BSc and PhD from
the University of Leeds. In 1986 he joined Courtaulds
Research as a Colour Physicist before returning to academia
in 1990 to work at the University of Keele. He worked as
a post-doctoral researcher and lecturer in the Department
of Communication and Neuroscience where he taught
and researched colour measurement, human colour vision,
computational imaging and image processing. In 1990
he was appointed as a Reader in Colour Imaging at the
Colour Imaging Institute of the University of Derby. He was
appointed as Professor of Colour Science and Technology
in the School of Design at the University of Leeds in 2003 where he currently teaches
and researches.
Hehaspublishedmorethan100refereedpapersintheareasofcolourimaging,colour
management,colourphysicsandcolourdesign.Hehasbeenactiveinprofessionalbodies
thatareconcernedwithcolour.Heisanactiveparticipantinconferencesorganisedbythe
SocietyofImagingSocietyandTechnology(IS&T)andservedonseveralorganisational
and technical committees. In 2008 he was awarded a Fellowship of the Society of
Dyers and Colourists and the Davies Medal from the Royal Photographic Society for
his research on digital colour imaging.
